Electron beam deflection structure



Jan. 19, 1960 c. H. MOULTON ELECTRON BEAM DEFLECTION STRUCTURE FiledSept. 17, 1956 FIG.2

26 I E 34 M20 1 FIG.3

oo c 0000 0000 DOUG OOQOOGDOOOOOOOOOOOQO INVEN TOR H. MOULTON CLIFFORDFIG. 6 BY ATTORNEYS United States Patent ELECTRON BEAM DEFLECTIONSTRUCTURE Clifiord H. Moulton, Portland, Oreg., assignor to Tehtronix,Inc., Portland, 0reg., a corporation of Oregon Application September 17,1956, Serial No. 610,101

11 Claims. (Cl. 315-23) This invention relates to a deflection structurefor a cathode ray tube and more particularly to an improved deflectionstructure in which a signal voltage is caused to travel along adeflection plate forming part of such structure at substantially thesame velocity as that of the electrons in the electron beam of the tubeso as to extend the frequency range and transient signal response ofsuch tube.

The structure of, the present invention is particularly useful incathode ray tubes for cathode ray oscilloscopes. Both horizontal andvertical deflection in such tubes is usually of the electrostatic type.That is to say, two pairs of deflection plates at right angles to eachother are usually employed with the individual plates of each pairpositioned on opposite sides of the beam of electrons. in order tosecure adequate deflection of the beam, the deflection plates must havesubstantial length in the direction of the beam. This places an upperlimit upon the frequencies of the signal voltage which can beeflectively impressed upon the vertical deflection plates. Also, sincetransient signal voltages involve extremely high frequencies, the lengthof the plates in the direction of electron travel also limits theaccuracy of the response of the cathode ray tube to such transientsignal voltages.

It will be apparent that maximum deflection for a Signal voltage ofgiven amplitude will occur when the transit time of an electron in thebeam along the length of the plates is less than the time correspondingto a half wave length of the signal voltage and that a partial orcomplete reversal of the deflection voltages on the vertical deflectionplates occurs when the transit time of the electron along the platesexceeds the time represented by such half wave. When the transit timebecomes equal to the time corresponding to a full wave of the signalvoltage, there is substantially equal deflection in opposite directionsto produce zero deflection. Such zero deflection also occurs atharmonics of the lowest frequency which produces zero deflection. Themagnitude of the deflection is therefore a function of frequency as wellas of amplitude of the signal voltage and the effects discussed abovebecome of importance at frequencies for which the transit time of anelectron along the deflection plates is a substantial fraction of theperiod corresponding to a wave length of the signal voltage.

In accordance with the present invention, a deflection structure isprovided in which the signal voltage is propagated along a deflectionplate in the direction of electron movement at a velocity which issubstantially equal to the velocity of the electrons in the beam.Furthermore, the structure provides for suppression of reflections ofsuch signal voltages so that the resulting deflections becomessubstantially independent of the frequency of the applied signal voltageand transient response is very materially improved. In a preferredembodiment of the invention, a deflection plate is provided which has aplurality of conducting elements extending transversely of the electronbeam. Each of such conducting elements has a surface forming part of thedeflection surface of the deflection plate and the conducting elementshave their ends connected together alternately on opposite sides of thedeflection plate so as to provide a zigzag path for the signal voltagepropagated along the plate. The electrical characteristics of thedeflection structure utilizing the plate can be made such that a signaltravels the length of the plate at the same speed of the electrons inthe electron beam and the signal voltage is eflective at all times toproduce a deflection force on the electrons in the beam.

The structure of the deflection plate of the present invention lendsitself to the provision of a deflection structure which has the samecharacteristic impedance as an input conductor, such as a coaxial cable.That is to say, the deflection plate of the present invention may bepositioned between a pair of conducting plate members so that thedeflection plate, in efiect, forms a continuation of the centralconductor of the coaxial cable and the conducting plate members,referred to, form an effective continuation of the outer conductor ofthe coaxial cable. In such a structure, the deflection plate of thepresent invention is positioned closer to one of such conducting platemembers than the other and diverges from such other conducting platemember from the entrance end of the structure for electrons toward theoutlet end for such electrons to provide a diverging passage between thedeflection plate and such other conducting plate member. The inductanceper unit length of the deflection structure containing the deflectionplate may be varied by varying the length of the transverse conductingelements and their spacing from each other and the capacitance per unitlength can be varied by varying the width of the deflection plate andthe associated conducting plate members and also the spacing between thedeflection plate and one of the conducting plate members. By properlyvarying the factors mentioned, the deflection plate structure may becaused to have the characteristic impedance of any of the usual flexiblecommercial coaxial cables employed in test instruments while, at thesame time, providing a velocity of signal voltage propagation along theplate which is within the range of velocities which can be imparted toelectrons in the electron beam. Also, the outlet end of the deflectionstructure can be terminated in the characteristic impedance of thecoaxial cable and deflection structure so that reflections of the signalvoltage back along the deflection plate and the coaxial cable aresubstantially eliminated.

It is therefore an object of the present invention to provide animproved deflection structure for cathode ray tubes which has improvedfrequency and transient response.

Another object of the invention is to provide an improved deflectionplate for the cathode ray tubes of oscilloscopes in which a signalvoltage is applied at one end of the deflection plate and travels alonga zigzag path so as to have a net velocity in the direction ofpropagation of electrons in the electron beam of the tube which issubstantially the same as that of the electrons in such beam.

Another object of the invention is to provide a deflection structure forthe beam of a cathode ray tube in which a signal is propagated along adeflection plate in the direction of the electrons in the electron beamof such tube at a rate substantially equal to the velocity of theelectrons in the beam and in which the deflection structure hassubstantially the same characteristic impedance as the connectorstructure for connecting said plate to a signal source and in which theother end of the deflection structure can be terminated in suchcharacteristic impedance.

A further object of the invention is to provide a deflection platestructure for a cathode ray tube in which a deflection plate ispositioned between a pair of conductpedance substantially the same asthat of a coaxial cable employed for impressing a signal upon one end ofthe deflection structure and in which adeflection plate causes thesignal voltage pressed thereonto travel in a zigzag path with a netVelocity of the direction of the electron beam substantially equal .tothe velocity of the electrons in such beam and in which such structureprovides for terminating the other end of the structure at thecharacteristic impedance of such structure. 2

Other objects and advantages of the invention will ap pear in thefollowing description of a preferred embodiment shown in the attacheddrawings of which:

Fig. 1 is a diagrammatic vertical cross section of a cathode ray tubeembodying the deflection structure of the present invention;

Fig. 2 is a vertical cross section through the deflection structure ofthe present invention and also diagrammatically showing the electricalconnections thereto;

Fig. 3 is a vertical cross section taken on the line 3-3 ofFig.2; i w

Fig. 4 is a plan of the deflection invention with parts broken away; 1

Fig. 5 is a plan of the deflection plate of the present invention in itscondition before installation in the deflection plate structure of Figs.2 to 4; and

Fig. 6 is a side elevation view of one of the insulating supportingplates for the deflection plate of Fig.5.

Referring more particularly to the drawings, the deflection platestructure ltl of the present invention is positioned within the glassenvelope 12 of a cathode ray tube having a phosphor coating 14 on theinterior of the large end of the envelope 12. The envelope 12 of thetube is provided with a conventional plug 16 having the usual pins 17for insertion into a socket, the pins 17 furnishing electricalconnections to an electron gun 18 which may be a conventional typeproviding a beam 243 of electrons which first pass between conventionalhorizontal deflection plates 22 and then through .the verticaldeflection structure of the present invention andthereafter impinge uponthe screen formed by the phosphor coating 14 and the end of the envelope12 of the tube. The deflection structure 10 includes a deflection plate24 positioned between a pair of conductingplate members 26 and 28 withthe deflection plate 24 nearer the conducting plate member 26 than theconducting plate member 28. The electron beam indicated by the line 20in Fig. 2, enters the deflection structure at the entrance end 3}thereof. It passes between the deflection plate .2 and the conductingplate member 28 and leaves the deflection structure 10 through theoutlet end 31 of the deflection structure. During its passage throughthe deflection structure, the beam 20 is deflected vertically in Fig. 2by a signal voltage propagated along the deflection plate 24 from theinlet end 34 of the deflection structuretothe outlet end 31.

The preferred form of the deflection plate 24 is most clearly shown inFigs. 4 and 5 Such plate is a thin sheet of conducting material,preferably a spring metal which will withstand bending, for example, asheet of Phosphor bronze. The deflection structure 10, including boththe deflection plate 24 and the plates 26 and 28, preferably tapers soas to be wider at its outlet end 31 than at its inlet end 30. Thedeflection plate 24 has a plurality of riarrowslots 32 extendinginwardly alternately from opposite edges thereof, theinner ends of theslots overlapping to provide laterially extending conductor elements 33which extend transversely ofthe beam of electrons 20 and provide azigzag path for a signal voltage propagated alo ng the deflection platefrom the inlet end 30 of the structure to the outlet end thereof. In theplate shown, the conductor elernen ts are all of the same length but thewidth'of the elements is made progressively smaller and the width of theslots between such elements correspondingly larger from the inlet to theoutl l structure of the present of the deflection structure. Theportions of the deflection plate 24 between the slots at the oppositeedges of the deflection plate terminate in small support tabs 34 andsuch support tabs engage side support elements 36 in the form of thinsheets of insulating material, for example, mica. The support elements36 are of substantially the same length as the deflection plate 24 andconducting plate members 26 and 28 and have formed therein a pluralityof rows of small apertures 38 and 39. The row of apertures 38 ispositioned between t'wo rows of apertures 3) and nearer one of the rowsof apertures 39. The apertures 38'are' spaced to correspond to the tabs34 on the deflection plate 2.4 and such tabs are inserted into theaper'tures38 of supporting'platesso at each side of the deflection plate24. The tabs 34 are then bent over as shown in Fig. 3. The twoconducting plate members 26 and 28 are also provided with similar tabs34 which extend through the apertures 39 in the support element 36 andare bent'over as'shown in Fig. 3. This structure providesa rigid boxlikestructure in which the deflection plate 24 is rigidly supported by thesupport elements 3.6 in properly spaced relationship with the conductingplate members .26 and 28 which are also rigidly supported by the supportelements 36. The support elements 36 may be supp'orted'within theenvelope 12 of the cathode ray tube in any desired manner. The envelope12 may be provided with a suitable connector structure 42 adjacent theinlet end '33 of the deflection structure 10 providing for externalconnection to the deflection plate 24 and conducting plate members 26and 28. Also, the envelope 12 may be provided with a connector structure44 adjacent the outlet end 31 of the defiection structure 10, theconnector structures each having a pair of conductors extending throughthe walls of the envelope 12 and sealed therein in anysuitable orconventional manner.

As indicated in Fig. 2, the central conductor 46 of a coaxial cable 48may be connected to the deflection plate 24 at the inlet end 30 of thedeflection structure and the grounded outer cylindrical conductor 0 maybe connccted to the conducting plate members 26 and 28. At the outletend 31 of such deflection structure 10, the conducting plate members 26and 28 maybe connected together and also preferably to ground. Theoutlet end of the deflection plate 214 are also connected to theconducting plate members 2t? and 28 through a resistor 52 whichpreferably has a" value of resistance equal to the characteristicimpedance of the coaxial cable The resistor 52 may obviously'bepositioned internally of the envelope 12 but the structure shownin Fig.1 provides for external connection of the defl ron structure to theresistor 52.

The characteristic impedance of the deflection structure 10 may be rnadesubstantially the same as that of the coaxial cable 48 or other transmission line employed for supplying a signal voltag e to the inlet endof the deflection structure. That is to say, the characteristicimpedance of the deflection structure is a function of its inductanceper unit length andits capacitance per unit length, The inductance perunit lerigtli li i y be varied over a substantial range by varying'th'elength and width of the slots 32 and, similarly, the capacitance perunit length may be varied over a considerable'r'a'nge by varying thewidth of the deflection plate 24 and conducting plate members 26 and 28and also varyingthe distance between the deflection plate 24 and theconducting plate member 26. It is entirely possible to provide adeflection structure with a substantially constant characteristicimpedance equal to any of the coaxial cables commercially available andconventionally employed test instruments. Furthermore, suchcharacteristic impedances may be obtained while providing a net velocityof signal propagation in the dir ection of the travel of electrons inelectron beam 20, which is sr rbstantially the same as the velocity ofsuch electrons. Since the characteristic impedance of the deflectionstructure is substantially the same as that of the coaxial cable 48 andthe outlet end of the deflection structure is terminated in a resistorhaving a value substantially equal to such characteristic impedance,reflections of signal voltage are substantially eliminated and a signalvoltage applied through the coaxial cable 48 to the inlet end of thedeflection structure travels along the deflection plate 24 at the samespeed as the electrons in the beam 29 and is absorbed by the terminatingresistor 52. Vertical deflection in cathode ray oscilloscope tubeshaving the vertical deflection structure of the present inventionbecomes substantially independent of frequency from zero frequency to anupper cutoff frequency which may be several hundred megacycles and theresponse to transient signal voltages is very materially increased.

While the cathode ray tube illustrated is particularly adapted forconnection to the output of a single-ended amplifier or other signalsource having one side grounded, it is entirely possible to employ twoproperly spaced and diverging deflection plates 26 connected to theoutput of a push pull amplifier or other double-ended source of signalvoltage so that signal voltages in phase opposition travel along suchdeflection plates at the same speed as the electrons in the beam beingdeflected. Such a deflection structure may also have the samecharacteristic impedance as a balanced line connected to the input endof the deflection structure and the outlet end of such structure may besimilarly terminated in its characteristic impedance. Also, it isobvious that the relative positions of the vertical deflection structureand the horizontal deflection plates may be reversed so that theelectron beam first passes through the vertical deflection structure andthat either, or both, the vertical and horizontal deflection may beproduced by deflection structures having a zigzag path for a signalvoltage propagated along a deflection plate.

While I have disclosed the preferred embodiment of my invention, it isunderstood that the details thereof may be varied and that the scope ofthe invention is to be determined by the following claims.

I claim:

1. A deflection plate for causing deflection of a beam of electronstraveling in a predetermined direction along one surface of said platewhen a signal voltage is applied to said plate, said plate comprising aplurality of electrical conducting elements extending transversely ofsaid direction and spaced from each other in said direction to provide aseries of parallel elements with adjacent ends and narrow slots betweensaid elements, each of said elements having a surface in alignment witha'similar surface on the next adjacent elements to provide said onesurface, each of the intermediate elements of said series having one endelectrically conductively connected to the adjacent end of the nextpreceding element in said series and its other end electricallyconductively connected to the adjacent end of the next succeedingelement in said series to provide a zigzag electrically conductive pathalong said one surface for signal voltages propagated along said platein said direction.

2. A deflection plate for causing deflection of a beam of electronstraveling in a predetermined direction along one surface of said platewhen a signal voltage is applied to said plate, said plate being a sheetof electrical conducting material having a plurality of slots spacedfrom each other in said direction and each extending inwardly from oneedge of said plate and terminating short of the opposite edge of saidplate to provide a plurality of series connected electrically conductingelements, said elements extending transversely of said direction andbeing spaced from each other in said direction by said slots, alternateones of said slots extending inwardly from opposite edges of said plateto provide a zigzag electrically continuous conductive path through saidelements for signal voltages propagated along said plate in saiddirection.

3. A deflection plate for causing deflection of a beam of electronstraveling in a predetermined direction along one surface of said platewhen a signal voltage is applied to said plate, said plate being a thinplate of metal having a plurality of slots spaced from each other insaid direction and each extending inwardly from one edge of said plateand terminating short of the opposite edge of said plate to provide aplurality of series connected electrically conducting elements extendingtransversely of said direction and spaced from each other in saiddirection by said slots, alternate ones of said slots extending inwardlyfrom opposite edges of said plate to provide a zigzag electricallycontinuous conductive path through said elements for signal voltagespropagated along said plate in said direction.

4. A deflection plate for causing deflection of a beam of electronstraveling in a predetermined direction along one surface of said platewhen a signal voltage is applied to said plate, said plate being a thinsheet of metal having a greater length than width and tapering in widthfrom a relatively narrow width at one end to a relatively wider width atthe other end, said plate having a plurality of slots spaced from eachother in said direction and each extending inwardly from one edge ofsaid plate and terminating short of the opposite edge of said plate toprovide a plurality of elongated conducting elements extendingtransversely of said direction and spaced from each other in saiddirection by said slots, alternate ones of said slots extending inwardlyfrom opposite edges of said plate to provide a zigzag conductive paththrough said elements for signal voltages propagated along said plate insaid direction.

5. A deflection plate for causing deflection of a beam of electronstraveling in a predetermined direction along one surface of said platewhen a signal voltage is applied to said plate, said plate being a thinsheet of metal having a greater length than Width and tapering in widthfrom a relatively narrow width at one end to a relatively wider width atthe other end, said plate having a plurality of slots spaced from eachother in said direction and each extending inwardly from one side edgeof said plate and terminating short of the opposite edge of said plateto provide a plurality of elongated conducting elements extendingtransversely of said direction and spaced from each other in saiddirection by said slots, alternate ones of said slots extending inwardlyfrom opposite edges of said plate to provide a zigzag conductive paththrough said elements for signal voltages propagated along said plate insaid direction, said elements all being of substantially the same lengthand progressively decreasing in width from said one end to said otherend, said slots correspondingly progressively increasing in width fromsaid one end to said other end.

6. A deflection plate for causing deflection of a beam of electronstraveling in a predetermined direction along one surface of said platewhen a signal voltage is applied to said plate, said plate being a sheetof electrical conducting material having a plurality of slots spacedfrom each other in said direction and each extending inwardly from oneedge of said plate and terminating short of the opposite edge of saidplate to provide a plurality of electrical conducting elements extendingtransversely of said direction and spaced from each other in saiddirection by said slots, alternate ones of said slots extending inwardlyfrom opposite edges of said plate to provide electrically conductiveconnections between said elements alternately at opposite sides of saidplate and a zigzag electrically conductive path through said elementsfor signal voltages propagated along said plate in said direction, theconnections between said elements terminating in supporting tabsextending outwardly from the edges of said deflection plate forattachment to a supporting structure.

7. A deflection plate for causing deflection of a beam of electronstraveling in a predetermined direction along one surface of said platewhen a signal voltage is applied to said plate, said plate being of thinsheet metal having a plurality of slotsspaced from each other in saiddirection and each extending inwardly from one edge of said plate andterminating short of the oppositeedge ofsaid plate to provide aplurality ofelectiical conducting elements extendingtransversely of saiddirection and spaced from each other in said direction by said slots,alternate ones of said slots extending inwardly from oppositeedges ofsaid plate to provide electrically conductiveconnections between saidelements alternately at opposite sides of said plate and a electricallyconductive zigzag path through said elements for signal voltagespropagated along said plate in said direction, the connections betweensaid elements at said ends of said elements terminating in bendable uppng bs x e din ou ward y rom h edges of s id deflectibn P at fo a ta hmento a s p porting structure. I

8. A deflection structure for a cathode ray tube having means thereinfor producing a beam of electrons, said structure comprising a pair ofconducting plate members spaced from each other for receiv n said beambetween s plates, i Plate m m r .d er ins rqm-fiaeh ethe in thedirection 'of electron travel in said beam and providing inlet andoutlet ends for said beam, at third plate member positioned between saidconducting plate members and nearer one of said conducting plate membersthan the other so as to be positioned on one side of said beam, saidthird plate member being constrn cted of a plurality of conductingelements extendingtransversely of said beam and having adjacent ends andbeing spaced from each other in said direction by narrowslots to providea series of parallel elements, each of the intermediate elements of saidseries having one end conductively connected to the adjacent end of thenext precedingelement in said series and its other end conductively cnnec ted to the adjacent end of the next succeeding element in 'saidseries to provide a zigzag conductive paththrough said elements forsignal voltages propa ated ai ng said third plate member, and supportingmeans for said plate members. i i

9. A deflection structure for a cathode ray tube having means thereinfor producing a beam ofelectrons, said structure comprising a pair ofconducting plate members spaced from each other for receiving said'beambetween said plates, said plate members diverging from each other inthe direction of electron travel in' said beam and providing inlet andoutlet ends for said beam, a thiird' plate member positioned betweensaid'c'onducting plate members and nearer one of said conducting platemembers than the other so as to be'positioned on one side of said beam,said third plate member being constructed of a plurality of conductingelements extending transversely of said beam and having adjacent endsand being spaced from each other in said direction by narrow slots toprovide a series of parallel elements, each of the intermediate elementsof said series having one end conductively connected to the adjacent endof the next preceding element in said series and its other endconductively connected to the adjacent end of the next succeedingelement in said series to provide a zigzag conductive path through saidelements for signal voltages propagated along said third plate member,and supporting means for said plate members comprising insulatingmembers secured to and extending between the lateral edges of said platemembers, said plate members being wider adjacent said outlet end thanadjacent said inlet end.

10. A deflection structure for a cathode ray tube having means thereinfor producing a beam of electrons, said structure comprising a pair ofconducting plate members spaced from each other for receiving said beambetween said plates, said plate members diverging from each other in thedirection of electron travel in said beam and providing inlet and outletends for said beam, a third plate member positioned betweeen saidconducting plate members and nearer one of ,saidconducting plate membersthan theother so as rape positioned on one side of said beam, said thirdplate member being constructed of a plurality of conducting elementsextending transversely of said beam having adjacent ends and spaced fromeach other in said direction by narrow slots to provide a series ofparallel elements, each of the intermediate elements of said serieshaving one end conductively connected to the adjacent end of the nextpreceding element in said series and its other end conductivelyconnected to the adjacent end of the next succeeding element in saidseries to provide a zigzag conductive path through said element forsignal voltages propagated along said third plate member, supportingmeans for said plate members, conducting means extending to the exteriorof said tube from said inlet end to provide for impressing a signalvoltage between said third plate member and said conducting platemembers and conducting means extending to the exterior of said tube fromsaid outlet end.

11. A deflection system for a cathode ray tube having means therein forproducing a beam of electrons, said system including a deflectionstructure comprising a pair of conducting plate members spaced from eachother for receiving said beam between said plates, said plate membersdiverging from each other in the direction of electron travel in saidbeam and providing inlet and outlet ends for said beam, a third platemember positioned between said conducting plate members and nearer oneof said conducting plate members than the other so as to be positionedon one side of said beam, said third plate member being constructed of aplurality of conducting elements extending transversely of said beam andhaving adjacent ends and being spaced from each other in said directionby narrow slots to provide a series of parallel elements, each of theintermediate elements of said series having one end conductivelyconnected to the adjacent end of the next preceding element-in saidseries and its other end conductively connected to the adjacent end ofthe next succeeding element in said seriesto provide a zigzag conductivepath through said elements for signal voltages propagated along saidthird plate member, supporting means for said plate members, saiddeflection structure including conducting means extending to theexterior of said tube adjacent said inlet end of said structure toprovide for impressing a signal voltage between said third plate memberand said conducting plate members, a connector structure for connectingsaid conducting means to a' source of signal voltage, said deflectionstructure having substantially the same characteristic impedance as saidconnector structure, and means for terminating said outlet end of saiddeflection structure with a value of resistance substantially equal tosaid characteristic impedance.

References Cited in the file of this patent UNITED STATES PATENTS2,064,469 Haefi Dec. 15, 1936 2,195,456 Hollmann Apr. 2, 1940 2,293,539Gray Aug. 18, 1942 2,409,992 Strobel Oct. 22, 1946 2,535,317 Pierce Dec.26, 1950 2,609,520 Pierce Sept. 2, 1952 2,630,544 Tiley Mar. 3, 19532,698,398 Glinzton Dec; 28, 1954 2,708,236 Pierce May 10, 1955 2,827,588Guenard et a1 Mar. 18, 1958 2,832,001 Adler Apr. 22, 1958 UNITED STATESPATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 2922 074 Janaary l9i960 Clifford H Moulton It is hereby cer'ziiiied that error appears inthe prineed speciiicaiion oi" the above numbered pateni requiringc-orrec'tion and ihat *ihe said Letters Paizent should; read ascorrecied belowo Column 5 line 21 for "plates 26" read plates 24 Signedand sealed ihis 5H1 day of July 1960,

(SEAL) Atfiest:

KARL Ho AXLINE Attesting officer ROBERT C. WATSON Commissioner ofPatents

